Preheating and drying device

ABSTRACT

The preheater and dryer device has a housing and a first collector is disposed inside the housing. A feeding device extends into the housing and contains a material to be dried and preheated. A movable and hollow central conduit extends from the upper end of the housing to a bottom portion of the first collector. The central conduit carries a hot and dry air into the housing. A first and a second conical shield are attached to the central conduit. The central conduit is movable between a first open position and a second closed position. The second conical shield is tightly held against the first collector to close the bottom opening thereof when the central conduit is in the second closed position and the second conical shield is separated from the first collector when the central conduit is in the first open position.

PRIOR APPLICATIONS

This application is a U.S. national phase application based uponInternational Application No. PCT/SE01/00014, filed Jan. 5, 2001; whichclaims priority from U.S. Provisional Application No. 60/174,452; filedJan. 5, 2000.

TECHNICAL FIELD

The present invention relates to a preheating and drying device forpolymeric and other materials.

BACKGROUND AND SUMMARY OF THE INVENTION

Before a material, such as a polymeric material, is processed, it isimportant to remove contaminants and moisture from the material toprevent defects such as warping, uneven shrinkage and undesirablediscoloration. Many devices have been developed in the past that removesuch contaminants and moisture. However, such conventional devices areoften very expensive to manufacture, unreliable and require longproduction cycles. There is a need for an inexpensive and reliabledevice for heating and drying a material to remove contaminants andmoisture before it is further processed.

The preheating and drying device of the present invention has a housingand a first collector is disposed inside the housing. A feeding deviceextends into the housing and contains a material to be dried andpreheated. A movable and hollow central conduit extends from the upperend of the housing to a bottom portion of the first collector. Thecentral conduit carries a hot and dry air into the housing. A first anda second conical shields are attached to the central conduit. Thecentral conduit is movable between a first open position and a secondclosed position. The second conical shield is tightly held against thefirst collector to close the bottom opening thereof when the centralconduit is in the second closed position and the second conical shieldis separated from the first collector when the central conduit is in thefirst open position to permit the material to flow through the bottomopening.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-D are cross-sectional side views of the preheater of thepresent invention;

FIG. 2 is a side view of a second embodiment of the preheater of thepresent invention;

FIGS. 3A-D are cross-sectional side views of a third embodiment of thepreheater of the present invention; and

FIGS. 4A-F are cross-sectional side views of a fourth embodiment of thepresent invention.

DETAILED DESCRIPTION

With reference to FIGS. 1A-D, the preheater 20 includes a tight housing21. The preheater 20 has an electric motor 40 attached to a lid 23 ofthe housing 21. The motor 40 is in operative engagement with a rotatabledrying plate 42 via a drive shaft 44. The motor 40 operates at a certainfrequency pulse. By counting the pulses, it may be possible to determinethe amount of material 70 that has been deposited on the plate 42. Theplate 42 may have raised vertical side walls 43 that prevents thematerial 70 from being sucked out through the outlet hose 24. The motor40 rotates the drying plate 42 at a very constant and predeterminedrotational speed. The chute 18 has a bottom end 46 that is preciselypositioned above the plate 42. For example, the bottom end 46 may beabout 1 millimeter above the surface of the plate 42. Of course, thebottom end 46 may be closer or further away from the plate 42 such as2-5 millimeters, depending upon the feeding material used. In thepreferred embodiment, the material could an amino material such as amelamine, phenol or urea based material. Other feed material may also beused.

At a bottom end of the drive shaft 44 is a dust cone 48 attached. Thedust cone 48 is disposed inside a V-shaped container 50 with slantingside walls 52, 54. The side walls 52, 54 are preferably insulated toreduce any heat loss through conduction. The side wall 52 has a maximumlevel sensor 53 and a temperature sensor 55 located below the sensor 53.The container 50 has a bottom end 56 that has a raised air distributor58 located in the center of the bottom wall. The opening 58 leads into acylindrical vertical channel 60 that has an openable valve 62 disposedtherein.

The air hose 36 is connected to a heating unit 64 located at the inlet38 to heat the air flowing in the air hose 36. The hose 36 is in fluidcommunication with an inside conduit 66 that is connected to the airdistributor 58. A heat sensor 67 is located on the conduit 66 at theinlet 38 to control the temperature of the air in the conduit 66 that isheated by the heating unit 64. The air may reach a temperature of about100-120° C. and is extremely dry because the air has been dried in adehumidifier. The air may be as dry as −dp58° F. It is important to usevery dry air to enhance the drying or removing of moisture quickly fromthe material 70. The air flow in the conduit 66 may be significant. Forexample, the air flow may reach 180 m³/h. A side hose 68 extends fromthe conduit 66 to a point in the channel 60 that is below the valve 62.

In operation, a chute having a desirable inner diameter is selected. Thedistance between the bottom end 46 of the chute 18 and the top surfaceof the plate 42 is set to a desired level to predetermine the height ofthe volumetric dosage of the material 70 flowing in the chute 18. Thespeed of the motor 40 is also set to a desirable speed. The aboveparameters depend upon the conditions of the operation and the material70 used.

As the plate 42 rotates, the material 70 is deposited as a long stringon the plate 42. The material 70 could be in any suitable form such asin pellet or powder form. For example, the particles may be about 1-2millimeters. Slightly above the plate 42 a stationary scraper ordiverter 72 is attached to the lid 23 to divert or direct the material70 towards the middle of the plate 42. Between an inside diameter of theplate 42 and the outside of the shaft 44 an opening 74 is defined thatallows the material 70 to fall through and onto the dust cone 48. Theplate 42 is held to the shaft 44 by spokes 75.

An important feature of the present invention is that dust is sucked outthrough the outlet hose 24 when the material 70 is on the plate 42. Dustand other particles are also sucked out as the material 70 falls ontothe cone 48 as illustrated by dust clouds 76. In other words, thematerial 70 is heavier than some of the contaminates that are air born.The material 70 then falls onto the warm conduit 66 to further increasethe temperature of the material 70 by conduction (as best shown in FIG.2B). The material 70 then falls onto the closed valve 62.

The material 70 accumulates in the container 50 while being preheated bythe hot air exiting the conduit 66 at the distributor 58. Sometimes thematerial has poor conductivity and takes a long time to heat. However,certain materials should not be heated to more than about 70° C.,depending upon the material used, to prevent the start of a chemicalreaction in the material initiated by a latent catalyst, such as zincsulfate, that is mixed into the material 70. It is particularlyimportant that the material 70 is warm to help the catalyst later in theprocess because the material is so dry. Generally, some moisture in thematerial may promote the desired reaction once the material is in themold. However, the increased temperature of the material 70 compensatesfor the lack of moisture.

Because the air flow from the conduit 66 is significant, the upwardlyflowing air has a fluidizing effect on the material 70 disposed in thecontainer 50 while the material is being dried. It is important to notethat the warm air from the conduit 66 also warms up the plate 42 as theair flows upwardly in the housing 21. The plate 42 may have atemperature of about 50° C. so that the warm air also dries the material70.

The temperature sensor 55 monitors the temperature of the material 70and sends signals to the heater 64 when the material 70 is preheated inthe container 50. When the material 70 reaches the maximum level sensor53, the sensor 53 sends a shut off signal to the motor 40 to stoprotating the plate 42 and the flow of the material 70 in the chute 18 isterminated. Of course, the motor 40 may stop before the material 70reaches the sensor 53 if a predetermined amount of material 70, such as1 kilogram, has been ordered.

When the container 50 is filled and the temperature of the material 70is at a desired level as determined by the sensor 55, an open signal issent to the valve 62 to open the valve 62 and allow the material to flowinto a bottom reservoir 78 that has bottom openings 80 defined therein.It is advantageous to position the sensor 55 away from the distributor58 so that the sensor measures the temperature of the material 70without being unduly affected by the temperature of the incoming air inthe conduit 66. An added feature is that the valve 62 is sloping towardsthe side of the location of the sensor 55 so that the air is more likelyto flow on the right side of the container 50 because there is a shorteddistance from the bottom of the container to the top of the material 70on the right side of the container 50. This further reduces the riskthat the sensor 55 is too much affected by the temperature of theincoming air. Additionally, the suction of the outlet hose 24 is also onthe right side of the housing 21.

As best seen in FIG. 1C, hot air from the side hose 68 keeps thematerial 70 warm and dry while being in the reservoir 78. A suitable hotmold 94 is then placed below the openings 80 so that the heated material70 may flow into the mold. The mold should have a temperature of about130-170° C. and more preferably 140-150° C. to start the curing reactionof the material 70 depending upon which material 70 is being processed.Preferably, the pressure in the mold should be between about 250-350bar/cm². The preheater device also has an automatic cleaning feature sothat all the dust may be sucked up into a dust cyclone to prevent thedust from entering into the atmosphere.

FIG. 2 shows a second embodiment of the preheater device 300 of thepresent invention. The device 300 is similar to the above describedembodiments and only the most important differences are described. Thedevice 300 has an additional dosage mechanism 302 for fine adjustmentsof the dosage of the material 70 that is deposited into a mold 304. Thedosage mechanism 302 may also be used for feeding in the material intothe device. The mechanism 302 has horizontal pistons 306 that move backand forth in a horizontal cylinder 308 so that dosages of the material70 may be distributed in bottom chutes 310, 312 that are disposed abovethe mold 304. The effective length of the pistons 306 may be adjusted tomore precisely the determine the amount of the material 70 that ispermitted to enter the chutes 310, 312. One advantage of using thepistons is that the dosage is very accurate and there is less leakagethat undesirably may increase the moisture content in the material 70.

FIGS. 3A-3C show detailed cross-sectional side views of a thirdembodiment of a preheater 320 of the present invention. The preheater320 has a top feeder section 322 and a middle section 324 and a bottomsection 326. The section 322 is conical or triangular shaped and has anopenable and closeable valve 328 at a cylindrical bottom section 330thereof. The valve 328 is closed when the valve is in a horizontalposition and opened when the valve is in a vertical position so that amaterial 332 may flow through the valve 328.

Similarly, the middle section 324 is conical or triangular shaped andhas a level sensor 333 mounted at an upper end of the middle section 324that may close the valve 328 when a sufficient amount of material hasflown into the middle section 324. The section 324 has an openable valve334 at a cylindrical bottom section 336 thereof. The valve 334 may be ina closed position when the valve is in a horizontal position (see FIGS.3A, 3B,D) and in an opened position when the valve is in a verticalposition (see FIG. 3C). A portion 336 of the material 332 may be storedin the middle section 324 and may be released to the bottom section 326by opening the valve 334 so that the portion 336 is stored in the bottomsection 326 (see FIG. 3D).

The bottom portion 326 has a triangular shield 338 that partially orcompletely covers an opening 340 defined between the middle section 324and the bottom section 326. A narrow slit opening 341 is formed betweenthe shield 338 and the upper wall 362 to permit the material portion 336to flow therebetween. The shield 338 is heated by the up-flowing hot andextremely dry air as marked by arrows 342. The shield 338 is also a heatshield and prevents most of the hot dry air from flowing into the middlesection 324 to heat up the valve 334. If the valve 334 becomes too warmor hot then the material portion 336 may be adversely affected. The hotair flows out of the downwardly bent conduit 344 that has an open end346 that terminates at a central bottom area 348 of the bottom section326. The shield 338 also reduces the risk of the material portion 336flowing out through an exhaust opening 354. The exhaust opening 354 mayalso be defined in an openable and closeable lid of the device 300. Thehot air flows downwardly and bounces back off a closeable valve 350 at abottom portion 352 of the bottom section 326. The hot air, as marked bythe arrows 342, may flow out through the exhaust opening 354 defined atan upper end 356 of the bottom section 326. A separator 360 may hangdown from an upper wall 362 of the bottom section 326 to prevent theexhaust air from interfering with the material that lands on the shield338.

The valve 350 may be activated to open by a moisture content measurementdevice 351 located at the exhaust opening 354 that is designed to sendsignals to open the valve 350 when the exhaust air is sufficiently dry.The valve 350 may also be designed to open based on preset time periodsor based on a level sensor 355 disposed at the upper end of the unit326. It may be possible set up a control system so that if the unit 324contains material while a different batch is contained in the unit 326,then the valve 334 should not be permitted to open until the valve 350has been opened and the portion 336 has flown out of the unit 326 sothat the unit 326 is ready to receive a new batch of material to bedried.

In operation, the valve 328 is opened so that the portion 336 of thematerial 332 flows down into the middle section 324 and is held in thesection 324 by the closed valve 334. The valve 334 is then open when thelevel sensor 333 is activated and the portion 336 flows downwardly andlands on the shield 338 that spreads out the portion 336 for improvedairing and drying of the material portion 336. The shield 338 alsotransfers some heat to the portion 336 that lands on the shield 338 toenhance the drying process. Also, before landing on the valve 350 at thebottom of the bottom section 326, pieces 364 are exposed to the upwardlyflowing hot and very dry air. Lighter particles, moisture andcontaminants flow out through the exhaust opening 354 to improve thepurity of the pieces 364 of the portion 336. It is important to removecontaminants and moisture because they may discolor the finishedproduct.

When the entire batch of the portion 336 has landed in the bottomsection 326, the valve 350 may be opened to permit the portion 336 becollected for further use. It may be possible to eliminate the unit 324by providing the unit 322 with a level sensor or any other suitablemeasuring device such as a hopper feeder or screw feeder for conveyingnew material into the device 300.

With reference to FIGS. 4A-4F, a preheater and dryer device 400 has amaterial storage unit or feeding device 402 for storing a material 403disposed on one side of a longitudinal axis L. The unit 402 has aopenable and closeable valve 404 located in a middle segment of the unit402. A guiding portion or outlet portion 406 protrudes into a triangularshaped drying unit or collector 408. The unit 408 has a central verticalconduit 410 that extends form a top portion 412 to a narrowing bottomportion 414 of the unit 408. The unit 408 has slanting and upwardlydiverging inner walls 416. A triangular shaped shield 418 is mounted onthe conduit 410 so that bottom corners 420, 422 are adjacent to thewalls 416 so that gaps 424, 426 is formed therebetween.

A bottom end 428 of the conduit 410 has a triangular shaped valve 430mounted thereon so that hot and very dry air may flow inside the conduit410 and flow out at the bottom end 428 and bounce of the valve 430 andtravel upwardly, as indicated by the arrows 432, between the gaps 424,426 and out through an exhaust opening 456 defined at a right side ofthe upper end 412 of the unit 408.

The conduit 410 is connected, at its upper end, to a spring-biased andpneumatic adjustment cylinder mechanism 436. The mechanism 436 isbiasing the conduit 410 upwardly by springs 437 so that a slanting sidewall 457 of the valve 430 bears against acute angled corners 440, 442 atthe bottom of the side wall 414. The conduit 410 is hollow so that hotand very dry air may flow inside the conduit 410 as shown by the arrows411. Before the air enters the conduit 410, the air may be preheated.

Below the valve 430 is a storage unit 444 with an inwardly slopingbottom surface 446 leading to a portion arrangement 448. The arrangement448 has a handle 450 for opening and closing the arrangement 448 asdesired. It should be understood that the device 400 may be modified toinclude the dosage mechanism 302 so that the mechanism 302 may be usedfor feeding in the material into the device 400 and/or feeding out thedried and pure material at the bottom of the device 400.

In operation, when the valve 404 is opened, the material 403 fallsdownwardly through the guide 406 and onto the sidewall 416 and the upperouter wall 452 of the shield 418. The shield is heated by the upwardlyflowing hot air. The material 403 is guided through the opening 424disposed between the corner 420 of the shield 418 and the sidewall 416.

When the material 403 passes through the opening 424 the upwardlyflowing air distributes the material 403 into pieces 454 that gather onthe upside slanting wall 457 of the valve 430. The material cannot passinto the unit 444 because the valve 430 is closed. The materialcontinues to gather at the bottom 414 of the unit 408 until the storage402 is empty. Hot air continuously flows upwardly through the materialand exhaust gases flow out through the exhaust opening 456 to fluidizethe material until the material is sufficiently dry. Dust andcontaminants also flow out through the exhaust opening 456. The exhaustopening 456 may also be defined in an openable and closeable lid of thepreheater device 400. Similarly to the device in FIG. 3, the, dryness ofthe material may be measured indirectly by measuring the moisture of theexhaust gases at the opening 456. It should be noted that while thematerial is fluidized at the bottom of the conical section 408, the unit402 may be filled with a new batch of material.

When the material contained in the unit 408 is sufficiently dry, theconduit 410 and consequently the valve 430 may be urged downwardlyagainst the biasing force of the springs 437 so that the material mayflow from the unit 408 through gaps 458 formed between the valve 430 andthe corners 440, 442. The material is further distributed by the wall457 of the conical shaped valve 430. As best shown in FIG. 4D, when thevalve 430 is open, the shield 418 is urged against the sidewall toprevent too much hot air from escaping through the exhaust opening.Since hot and dry air continuously flow out through the bottom end ofthe conduit 410, the temperature increases in a closed space 460 definedbetween the walls 416 and the underside of the shield 418. This furtherdries the material before the material flows into the unit 444. Some airmay escape between a gap 462 formed between the shield 418 and the innerwall 416. The temperature should not be too high so that the materialmelts or reacts in a undesirable way.

When the material to be dried and preheated has a very low density thenit may be advantageous to modify the unit 408 from being conical tocylindrical so that the inner walls are vertical. For example,pulverized wood is more suitable dried in a cylindrical middle sectionunit.

Since the valve 430 is spring biased, the valve 430 may function as asafety valve during a dust or any other explosion inside the housing ifthe explosion force is greater than the biasing force of the springs437.

While the present invention has been described in accordance withpreferred compositions and embodiments, it is to be understood thatcertain substitutions and alterations may be made thereto withoutdeparting from the spirit and scope of the following claims.

I claim:
 1. A preheater and dryer device, comprising: a housing havingan upper end and a lower end; a first collector disposed inside thehousing, the first collector having a chamber and a bottom openingdefined therein and an inner wall; a feeding device attached to theupper end of the housing and extending into the housing, the feedingdevice containing a material to be preheated, the feeding device havingan openable valve; a movable central conduit extending from the upperend of the housing to a bottom portion of the first collector, thecentral conduit being hollow for permitting a hot and dry air to passtherethrough and into the housing; a first conical shield attached tothe central conduit, the conical shield being disposed below the feedingdevice, the first conical shield having bottom corners adjacent to theinner wall of the first collector; a second conical shield attached to abottom end of the central conduit below the first conical shield; andthe central conduit being movable between a first open position and asecond closed position, the second conical shield being tightly heldagainst the first collector to close the bottom opening thereof when thecentral conduit is in the second closed position and the second conicalshield being separated from the first collector when the central conduitis in the first open position to permit the material to flow through thebottom opening.
 2. The preheater and dryer device according to claim 1wherein, the housing has a second collector disposed below the bottomopening of the first collector.
 3. The preheater and dryer deviceaccording to claim 2 wherein, the second conical shield extends throughthe bottom opening and into the second collector.
 4. The preheater anddryer device according to claim 1 wherein, first collector is conicalshaped and the inner wall is disposed below an outlet of the feedingdevice.
 5. The preheater and dryer device according to claim 1 wherein,the central conduit is in operative engagement with a spring mechanismthat biases the central conduit into the second closed position.
 6. Thepreheater and dryer device according to claim 1 wherein, the centralconduit has an opening defined immediately above the second conicalshield so that the hot dry air is permitted to flow into the firstcollector.
 7. The preheater and dryer device according to claim 1wherein, housing has an exhaust opening defined therein that is remotefrom the feeding device.
 8. The preheater and dryer device according toclaim 1 wherein, the second conical shield has a bottom end that iswider than the bottom opening of the first collector.
 9. The preheaterand dryer device according to claim 1 wherein, the first conical shieldhas a width that is substantially similar to a width of the firstcollector.
 10. The preheater and dryer device according to claim 1wherein, the feeding device is eccentrically disposed on the housing andadjacent to the central conduit.